A number of mutations in the signal sequence region of the lamB gene have been isolated. In collaboration with M. Hofnung, Institute Pasteur, Paris, France, the DNA sequence of these mutations will be determined. This should reveal essential elements of the signal sequence and provide insight into the molecular mechanism of protein export. A number of suppressor mutations which specifically suppress signal sequence mutations will be isolated. A genetic and biochemical characterization of these suppressors may reveal other essential components of the protein export machinery. Using various lamB-lacZ fusions, conditional lethal selections will be performed in order to isolate mutants which are generally defective in the export of proteins. Techniques of gene fusion will be applied to other outer membrane proteins, such as the matrix proteins, in order to determine if different outer membrane proteins are localized by different mechanisms.